Project Summary Defects in neuroepithelial progenitor self-renewal and differentiation can result in profound neurodevelopmental disorders including devastating birth defects such as microcephaly. The long-term objective of the proposed studies is to understand how neuroepithelial progenitor cell self-renewal and differentiation are coordinated. This proposal specifically focuses on a long non-coding RNA (lncRNA) that is expressed early in mouse neuroepithelial progenitor cells and, as differentiation proceeds, the lncRNA transcript is processed to yield a microRNA that is involved in neuronal differentiation. Moreover, the lncRNA physically interacts with key microcephaly proteins but the functional relationship between the lncRNA and these proteins is unknown. The major questions addressed in three Aims are as follows. Aim 1 will test the hypothesis that the lncRNA functions - independent of the miRNA - in regulating neuroepithelial progenitor proliferation and survival. Aim 1 creates cell lines and mouse models with specific deletion mutations, including a small deletion of this locus observed in a patient with microcephaly, for functional studies. Aim 2 will explore the cellular mechanism underlying the microcephaly phenotype, preliminary data which suggests a mitotic arrest. Moreover, Aim 2 will address the hypothesis that the lncRNA functions as a scaffold to help maintain sister chromatid cohesion through its interactions with the Cohesin complex, which is also implicated in microcephaly. Aim 3 will explore the mechanism underlying the temporal-spatial difference between the lncRNA host transcript and the embedded miRNA. Our overall goal is to discover new mechanisms that coordinate neuroepithelial progenitor cell proliferation and differentiation, as well as to decipher how this unexplored lncRNA mechanistically acts to allow normal brain growth. Harnessing the potential of neuroepithelial progenitor cells holds promise for the treatment of neuronal injury and neurodegenerative diseases, and dysfunction of neuroepithelial progenitors is at the root of numerous neurological disorders. Our studies will provide mechanistic links between a novel lncRNA and known microcephaly proteins to greatly extend our knowledge of this profound brain disorder.